/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkSmartVolumeMapper.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include <cassert>

#include "vtkCellData.h"
#include "vtkCellDataToPointData.h"
#include "vtkColorTransferFunction.h"
#include "vtkContourValues.h"
#include "vtkDataArray.h"
#include "vtkEventForwarderCommand.h"
#include "vtkFixedPointVolumeRayCastMapper.h"
#include "vtkGPUVolumeRayCastMapper.h"
#include "vtkImageData.h"
#include "vtkImageMagnitude.h"
#include "vtkImageResample.h"
#include "vtkOSPRayVolumeInterface.h"
#include "vtkObjectFactory.h"
#include "vtkPiecewiseFunction.h"
#include "vtkPointData.h"
#include "vtkPointDataToCellData.h"
#include "vtkRectilinearGrid.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"
#include "vtkSmartVolumeMapper.h"
#include "vtkUniformGrid.h"
#include "vtkVolume.h"
#include "vtkVolumeProperty.h"

vtkStandardNewMacro(vtkSmartVolumeMapper);

//------------------------------------------------------------------------------
// Constructor
//------------------------------------------------------------------------------
vtkSmartVolumeMapper::vtkSmartVolumeMapper()
  : VectorMode(DISABLED)
{
  // Default for Window / Level - no adjustment
  this->FinalColorWindow = 1.0;
  this->FinalColorLevel = 0.5;

  // Our render mode is undefined at this point
  this->CurrentRenderMode = vtkSmartVolumeMapper::UndefinedRenderMode;

  // Nothing is initialized and we assume nothing is supported
  this->Initialized = 0;
  this->GPUSupported = 0;
  this->RayCastSupported = 0;
  this->LowResGPUNecessary = 0;
  this->InterpolationMode = VTK_RESLICE_CUBIC;

  // If the render window has a desired update greater than or equal to the
  // interactive update rate, we apply certain optimizations to ensure that the
  // rendering is interactive.
  this->InteractiveUpdateRate = 1.0;
  // Enable checking whether the render is interactive and use the appropriate
  // sample distance for rendering
  this->InteractiveAdjustSampleDistances = 1;

  // Initial sample distance
  this->AutoAdjustSampleDistances = 1;
  this->SampleDistance = -1.0;

  // Create all the mappers we might need
  this->RayCastMapper = vtkFixedPointVolumeRayCastMapper::New();

  this->GPUMapper = vtkGPUVolumeRayCastMapper::New();
  this->MaxMemoryInBytes = this->GPUMapper->GetMaxMemoryInBytes();
  this->MaxMemoryFraction = this->GPUMapper->GetMaxMemoryFraction();

  this->GPULowResMapper = vtkGPUVolumeRayCastMapper::New();

  // This is the resample filter that may be used if we need
  // a lower resolution version of the input for GPU rendering
  this->GPUResampleFilter = vtkImageResample::New();

  // Compute the magnitude of a 3-component image for the SingleComponentMode
  this->ImageMagnitude = nullptr;
  this->InputDataMagnitude = vtkImageData::New();

  // Turn this on by default - this means that the sample spacing will be
  // automatically computed from the spacing of the input data. This is
  // also true for the GPU ray cast mapper.
  this->RayCastMapper->LockSampleDistanceToInputSpacingOn();
  this->GPUMapper->LockSampleDistanceToInputSpacingOn();
  this->GPUMapper->SetComputeNormalFromOpacity(this->ComputeNormalFromOpacity);
  this->GPUMapper->SetGlobalIlluminationReach(this->GlobalIlluminationReach);
  this->GPUMapper->SetVolumetricScatteringBlending(this->VolumetricScatteringBlending);

  // Default to the default mode - which will use the best option that
  // is supported by the hardware
  this->RequestedRenderMode = vtkSmartVolumeMapper::DefaultRenderMode;

  // Keep track of what blend mode we had when we initialized and
  // checked for hardware support - we need to recheck if the blend
  // mode changes
  this->InitializedBlendMode = -1;

  // Create the forwarding command
  vtkEventForwarderCommand* cb = vtkEventForwarderCommand::New();
  cb->SetTarget(this);

  // Now forward the ray caster's events
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperRenderStartEvent, cb);
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperRenderEndEvent, cb);
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperRenderProgressEvent, cb);
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperComputeGradientsStartEvent, cb);
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperComputeGradientsEndEvent, cb);
  this->RayCastMapper->AddObserver(vtkCommand::VolumeMapperComputeGradientsProgressEvent, cb);

  // And the GPU mapper's events
  // Commented out because too many events are being forwarded
  // put back in after that is fixed
  /***
  this->GPUMapper->AddObserver(vtkCommand::VolumeMapperRenderStartEvent, cb);
  this->GPUMapper->AddObserver(vtkCommand::VolumeMapperRenderEndEvent, cb);
  this->GPUMapper->AddObserver(vtkCommand::VolumeMapperRenderProgressEvent, cb);
  ***/

  // And the low res GPU mapper's events
  // Commented out because too many events are being forwarded
  // put back in after that is fixed
  /***
  this->GPULowResMapper->AddObserver(vtkCommand::VolumeMapperRenderStartEvent, cb);
  this->GPULowResMapper->AddObserver(vtkCommand::VolumeMapperRenderEndEvent, cb);
  this->GPULowResMapper->AddObserver(vtkCommand::VolumeMapperRenderProgressEvent, cb);
  ***/

  cb->Delete();

  this->OSPRayMapper = nullptr;

  this->Transfer2DYAxisArray = nullptr;

  this->LastInput = nullptr;
  this->LastFilterInput = nullptr;
}

//------------------------------------------------------------------------------
// Destructor
//------------------------------------------------------------------------------
vtkSmartVolumeMapper::~vtkSmartVolumeMapper()
{
  if (this->RayCastMapper)
  {
    this->RayCastMapper->Delete();
    this->RayCastMapper = nullptr;
  }
  if (this->GPUMapper)
  {
    this->GPUMapper->Delete();
    this->GPUMapper = nullptr;
  }
  if (this->GPULowResMapper)
  {
    this->GPULowResMapper->Delete();
    this->GPULowResMapper = nullptr;
  }
  if (this->GPUResampleFilter)
  {
    this->GPUResampleFilter->Delete();
    this->GPUResampleFilter = nullptr;
  }
  if (this->ImageMagnitude)
  {
    this->ImageMagnitude->Delete();
    this->ImageMagnitude = nullptr;
  }
  if (this->InputDataMagnitude)
  {
    this->InputDataMagnitude->Delete();
    this->InputDataMagnitude = nullptr;
  }
  if (this->OSPRayMapper)
  {
    this->OSPRayMapper->Delete();
    this->OSPRayMapper = nullptr;
  }

  this->SetTransfer2DYAxisArray(nullptr);

  this->LastInput = nullptr;
  this->LastFilterInput = nullptr;
}

//------------------------------------------------------------------------------
// The Render method will determine the render mode and then render using the
// appropriate mapper. If the render mode is invalid (the user explicitly
// chooses something that is not supported) the render will silently fail.
//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::Render(vtkRenderer* ren, vtkVolume* vol)
{
  // Compute the render mode based on the requested
  // render mode, available hardware, and render window's
  // desired update rate
  this->ComputeRenderMode(ren, vol);

  vtkGPUVolumeRayCastMapper* usedMapper = nullptr;

  switch (this->CurrentRenderMode)
  {
    case vtkSmartVolumeMapper::RayCastRenderMode:
      if (this->InteractiveAdjustSampleDistances)
      {
        this->RayCastMapper->SetAutoAdjustSampleDistances(
          ren->GetRenderWindow()->GetDesiredUpdateRate() >= this->InteractiveUpdateRate);
      }
      else
      {
        this->RayCastMapper->SetAutoAdjustSampleDistances(this->AutoAdjustSampleDistances);
      }
      this->RayCastMapper->Render(ren, vol);
      break;
    case vtkSmartVolumeMapper::GPURenderMode:
      if (this->LowResGPUNecessary)
      {
        usedMapper = this->GPULowResMapper;
      }
      else
      {
        usedMapper = this->GPUMapper;
      }
      if (this->InteractiveAdjustSampleDistances)
      {
        usedMapper->SetAutoAdjustSampleDistances(
          ren->GetRenderWindow()->GetDesiredUpdateRate() >= this->InteractiveUpdateRate);
      }
      else
      {
        usedMapper->SetAutoAdjustSampleDistances(this->AutoAdjustSampleDistances);
      }
      usedMapper->Render(ren, vol);
      break;
    case vtkSmartVolumeMapper::OSPRayRenderMode:
      if (!this->OSPRayMapper)
      {
        this->OSPRayMapper = vtkOSPRayVolumeInterface::New();
      }
      this->OSPRayMapper->Render(ren, vol);
      break;
    case vtkSmartVolumeMapper::InvalidRenderMode:
      // Silently fail - a render mode that is not
      // valid was selected so we will render nothing
      break;
    default:
      vtkErrorMacro("Internal Error!");
      break;
  }
}

//------------------------------------------------------------------------------
// Initialize the render
// We need to determine whether the GPU or CPU mapper are supported
// First we need to know what input scalar field we are working with to find
// out how many components it has. If it has more than one and we are considering
// them to be independent components, then only GPU Mapper will be supported.
//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::Initialize(vtkRenderer* ren, vtkVolume* vol)
{
  vtkDataSet* input = this->GetInput();
  if (!input)
  {
    this->Initialized = 0;
    return;
  }

  int usingCellColors = 0;
  vtkDataArray* scalars = vtkSmartVolumeMapper::GetScalars(input, this->ScalarMode,
    this->ArrayAccessMode, this->ArrayId, this->ArrayName, usingCellColors);

  if (!scalars)
  {
    vtkErrorMacro("Could not find the requested vtkDataArray! "
      << this->ScalarMode << ", " << this->ArrayAccessMode << ", " << this->ArrayId << ", "
      << this->ArrayName);
    this->Initialized = 0;
    return;
  }

  int const numComp = scalars->GetNumberOfComponents();
  this->RayCastSupported = (usingCellColors || numComp > 1) ? 0 : 1;

  if (!this->RayCastSupported &&
    this->RequestedRenderMode == vtkSmartVolumeMapper::RayCastRenderMode)
  {
    vtkWarningMacro(
      "Data array " << this->ArrayName
                    << " is not supported by"
                       "FixedPointVolumeRCMapper (either cell data or multiple components).");
  }

  // Make the window current because we need the OpenGL context
  vtkRenderWindow* win = ren->GetRenderWindow();
  win->MakeCurrent();

  this->GPUSupported = this->GPUMapper->IsRenderSupported(win, vol->GetProperty());
  this->Initialized = 1;
  this->InitializedBlendMode = this->GetBlendMode();
  this->SupportStatusCheckTime.Modified();
}

//------------------------------------------------------------------------------
// Compute the render mode based on what hardware is available, what the user
// requested as a render mode, and the desired update rate of the render window
//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ComputeRenderMode(vtkRenderer* ren, vtkVolume* vol)
{
  // If we are already initialized, and the volume,
  // volume's input, and volume's property have not
  // changed since last time we computed the render mode,
  // then we don't need to initialize again
  if (!(this->Initialized && this->SupportStatusCheckTime.GetMTime() > this->GetMTime() &&
        this->SupportStatusCheckTime.GetMTime() > vol->GetProperty()->GetMTime() &&
        this->SupportStatusCheckTime.GetMTime() > this->GetInput()->GetMTime() &&
        this->InitializedBlendMode == this->GetBlendMode()))
  {
    this->Initialize(ren, vol);
  }

  // Use this as the initial state to simplify the code below
  this->CurrentRenderMode = vtkSmartVolumeMapper::InvalidRenderMode;

  if (!this->GetInput())
  {
    return;
  }

  double scale[3];
  double spacing[3];
  if (auto imData = vtkImageData::SafeDownCast(this->GetInput()))
  {
    imData->GetSpacing(spacing);
  }
  else if (auto rectGrid = vtkRectilinearGrid::SafeDownCast(this->GetInput()))
  {
    // compute average spacing along each dimension
    double bounds[6];
    rectGrid->GetBounds(bounds);
    int dims[3];
    rectGrid->GetDimensions(dims);
    for (int i = 0; i < 3; ++i)
    {
      spacing[i] = (bounds[2 * i + 1] - bounds[2 * i]) / dims[i];
    }
  }

  // Compute the sample distance based on dataset spacing.
  // It is assumed that a negative SampleDistance means the user would like to
  // compute volume mapper sample distance based on data spacing.
  if (this->SampleDistance < 0)
  {
    this->SampleDistance = static_cast<float>((spacing[0] + spacing[1] + spacing[2]) / 6.0);
  }

  vtkRenderWindow* win = ren->GetRenderWindow();

  switch (this->RequestedRenderMode)
  {
    // Requested ray casting - OK as long as it is supported
    // This ray caster is a software mapper so it is supported as
    // we aren't attempting to render cell scalars
    case vtkSmartVolumeMapper::RayCastRenderMode:
      if (this->RayCastSupported)
      {
        this->CurrentRenderMode = vtkSmartVolumeMapper::RayCastRenderMode;
      }
      break;

    // Requested GPU - OK as long as it is supported
    case vtkSmartVolumeMapper::GPURenderMode:
      if (this->GPUSupported)
      {
        this->CurrentRenderMode = vtkSmartVolumeMapper::GPURenderMode;
      }
      break;

      // Requested default mode - select GPU if supported, otherwise RayCast
    case vtkSmartVolumeMapper::DefaultRenderMode:
      // Go with GPU rendering if it is supported
      if (this->GPUSupported)
      {
        this->CurrentRenderMode = vtkSmartVolumeMapper::GPURenderMode;
      }
      else if (this->RayCastSupported)
      {
        this->CurrentRenderMode = vtkSmartVolumeMapper::RayCastRenderMode;
      }
      break;

    case vtkSmartVolumeMapper::OSPRayRenderMode:
      this->CurrentRenderMode = vtkSmartVolumeMapper::OSPRayRenderMode;
      break;

      // This should never happen since the SetRequestedRenderMode
      // protects against invalid states
    default:
      vtkErrorMacro("Internal Error: Invalid RequestedRenderMode");
      break;
  }

  switch (this->CurrentRenderMode)
  {
    // We are rendering with the vtkFixedPointVolumeRayCastMapper
    case vtkSmartVolumeMapper::RayCastRenderMode:
      if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_NAME)
      {
        this->RayCastMapper->SelectScalarArray(this->ArrayName);
      }
      else if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_ID)
      {
        this->RayCastMapper->SelectScalarArray(this->ArrayId);
      }
      this->RayCastMapper->SetScalarMode(this->GetScalarMode());
      this->ConnectMapperInput(this->RayCastMapper);
      this->RayCastMapper->SetClippingPlanes(this->GetClippingPlanes());
      this->RayCastMapper->SetCropping(this->GetCropping());
      this->RayCastMapper->SetCroppingRegionPlanes(this->GetCroppingRegionPlanes());
      this->RayCastMapper->SetCroppingRegionFlags(this->GetCroppingRegionFlags());
      this->RayCastMapper->SetBlendMode(this->GetBlendMode());
      this->RayCastMapper->SetFinalColorWindow(this->FinalColorWindow);
      this->RayCastMapper->SetFinalColorLevel(this->FinalColorLevel);
      this->RayCastMapper->SetSampleDistance(this->SampleDistance);
      break;

    // We are rendering with the vtkGPUVolumeRayCastMapper
    case vtkSmartVolumeMapper::GPURenderMode:
      if (this->VectorMode == DISABLED)
      {
        // If the internal Magnitude data is not being used, then
        // set the array selection of the original input.
        if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_NAME)
        {
          this->GPUMapper->SelectScalarArray(this->ArrayName);
        }
        else if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_ID)
        {
          this->GPUMapper->SelectScalarArray(this->ArrayId);
        }
        this->GPUMapper->SetScalarMode(this->GetScalarMode());
        this->ConnectMapperInput(this->GPUMapper);
      }
      else
      {
        // Adjust the input or component weights depending on the
        // active mode.
        this->SetupVectorMode(vol);
      }

      this->GPUMapper->SetMaxMemoryInBytes(this->MaxMemoryInBytes);
      this->GPUMapper->SetMaxMemoryFraction(this->MaxMemoryFraction);
      this->GPUMapper->SetClippingPlanes(this->GetClippingPlanes());
      this->GPUMapper->SetCropping(this->GetCropping());
      this->GPUMapper->SetCroppingRegionPlanes(this->GetCroppingRegionPlanes());
      this->GPUMapper->SetCroppingRegionFlags(this->GetCroppingRegionFlags());
      this->GPUMapper->SetBlendMode(this->GetBlendMode());
      this->GPUMapper->SetFinalColorWindow(this->FinalColorWindow);
      this->GPUMapper->SetFinalColorLevel(this->FinalColorLevel);
      this->GPUMapper->SetSampleDistance(this->SampleDistance);
      this->GPUMapper->SetTransfer2DYAxisArray(this->Transfer2DYAxisArray);
      this->GPUMapper->SetComputeNormalFromOpacity(this->ComputeNormalFromOpacity);
      this->GPUMapper->SetGlobalIlluminationReach(this->GlobalIlluminationReach);
      this->GPUMapper->SetVolumetricScatteringBlending(this->VolumetricScatteringBlending);

      // Make the window current because we need the OpenGL context
      win->MakeCurrent();

      // Now we need to find out if we need to use a low resolution
      // version of the mapper for interactive rendering. This is true
      // if the GPU mapper cannot hand the size of the volume.
      this->GPUMapper->GetReductionRatio(scale);

      // if any of the scale factors is not 1.0, then we do need
      // to use the low res mapper for interactive rendering
      if (scale[0] != 1.0 || scale[1] != 1.0 || scale[2] != 1.0)
      {
        this->LowResGPUNecessary = 1;
        this->ConnectFilterInput(this->GPUResampleFilter);
        this->GPUResampleFilter->SetInterpolationMode(this->InterpolationMode);
        this->GPUResampleFilter->SetAxisMagnificationFactor(0, scale[0] / 2.0);
        this->GPUResampleFilter->SetAxisMagnificationFactor(1, scale[1] / 2.0);
        this->GPUResampleFilter->SetAxisMagnificationFactor(2, scale[2] / 2.0);

        this->GPULowResMapper->SetMaxMemoryInBytes(this->MaxMemoryInBytes);
        this->GPULowResMapper->SetMaxMemoryFraction(this->MaxMemoryFraction);

        this->GPULowResMapper->SetInputConnection(this->GPUResampleFilter->GetOutputPort());
        this->GPULowResMapper->SetClippingPlanes(this->GetClippingPlanes());
        this->GPULowResMapper->SetCropping(this->GetCropping());
        this->GPULowResMapper->SetCroppingRegionPlanes(this->GetCroppingRegionPlanes());
        this->GPULowResMapper->SetCroppingRegionFlags(this->GetCroppingRegionFlags());
        this->GPULowResMapper->SetBlendMode(this->GetBlendMode());
        this->GPULowResMapper->SetFinalColorWindow(this->FinalColorWindow);
        this->GPULowResMapper->SetFinalColorLevel(this->FinalColorLevel);
        this->GPULowResMapper->SetSampleDistance(this->SampleDistance);
      }
      else
      {
        this->LowResGPUNecessary = 0;
      }

      break;

    case vtkSmartVolumeMapper::OSPRayRenderMode:
      break;

      // The user selected a RequestedRenderMode that is
      // not supported. In this case the mapper will just
      // silently fail.
    case vtkSmartVolumeMapper::InvalidRenderMode:
      break;

      // This should never happen since we don't set the CurrentRenderMode
      // to anything other than the above handled options
    default:
      vtkErrorMacro("Internal Error: Invalid CurrentRenderMode");
      break;
  }
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ComputeMagnitudeCellData(vtkDataSet* input, vtkDataArray* arr)
{
  vtkImageData* imData = vtkImageData::SafeDownCast(input);
  if (!imData)
  {
    // TODO: Support image magnitude calculation for rectilinear grids
    return;
  }

  vtkNew<vtkImageData> tempInput;
  tempInput->ShallowCopy(imData);

  tempInput->GetCellData()->SetActiveAttribute(arr->GetName(), vtkDataSetAttributes::SCALARS);

  // vtkImageMagnitude can only process point data so, data is transformed first
  // to points and then back to cells.
  vtkNew<vtkCellDataToPointData> cellToPoints;
  cellToPoints->SetInputData(tempInput);
  cellToPoints->Update();
  tempInput->ShallowCopy(cellToPoints->GetOutput());

  const int id =
    tempInput->GetPointData()->SetActiveAttribute(arr->GetName(), vtkDataSetAttributes::SCALARS);
  if (id < 0)
  {
    vtkErrorMacro("Failed to set the active attribute in vtkImageMagnitude's input"
                  " (from cellToPoints)!");
    return;
  }

  this->ImageMagnitude->SetInputData(tempInput);
  this->ImageMagnitude->Update();

  vtkNew<vtkPointDataToCellData> pointsToCells;
  pointsToCells->SetInputConnection(this->ImageMagnitude->GetOutputPort());
  pointsToCells->Update();
  this->InputDataMagnitude->ShallowCopy(pointsToCells->GetOutput());
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ComputeMagnitudePointData(vtkDataSet* input, vtkDataArray* arr)
{
  vtkImageData* imData = vtkImageData::SafeDownCast(input);
  if (!imData)
  {
    // TODO: Support image magnitude calculation for rectilinear grids
    return;
  }
  vtkNew<vtkImageData> tempInput;
  tempInput->ShallowCopy(imData);

  const int id =
    tempInput->GetPointData()->SetActiveAttribute(arr->GetName(), vtkDataSetAttributes::SCALARS);
  if (id < 0)
  {
    vtkErrorMacro("Failed to set the active attribute in vtkImageMagnitude's input!");
    return;
  }

  this->ImageMagnitude->SetInputData(tempInput);
  this->ImageMagnitude->Update();
  this->InputDataMagnitude->ShallowCopy(this->ImageMagnitude->GetOutput());
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetupVectorMode(vtkVolume* vol)
{
  vtkDataSet* input = this->GetInput();
  if (!input)
  {
    vtkErrorMacro("Failed to setup vector rendering mode! No input.");
  }

  int isCellData = 0;
  vtkDataArray* dataArray = vtkSmartVolumeMapper::GetScalars(
    input, this->ScalarMode, this->ArrayAccessMode, this->ArrayId, this->ArrayName, isCellData);
  if (!dataArray)
  {
    vtkErrorMacro("Failed to locate data array.");
    return;
  }

  int const numComponents = dataArray->GetNumberOfComponents();
  switch (this->VectorMode)
  {
    case MAGNITUDE:
    {
      // ParaView sets mode as MAGNITUDE when there is a single component,
      // so check whether magnitude makes sense.
      if (numComponents > 1)
      {
        // Recompute magnitude if not up to date
        if (!this->ImageMagnitude ||
          input->GetMTime() > this->ImageMagnitude->GetOutput()->GetMTime())
        {
          if (!this->ImageMagnitude)
          {
            this->ImageMagnitude = vtkImageMagnitude::New();
          }

          // Proxy dataset (set the active attribute for the magnitude filter)
          if (isCellData)
          {
            this->ComputeMagnitudeCellData(input, dataArray);
          }
          else
          {
            this->ComputeMagnitudePointData(input, dataArray);
          }
        }

        if (this->InputDataMagnitude->GetMTime() > this->MagnitudeUploadTime)
        {
          this->GPUMapper->SetInputDataObject(this->InputDataMagnitude);
          this->GPUMapper->SelectScalarArray("Magnitude");
          this->MagnitudeUploadTime.Modified();
        }
      }
      else
      {
        // Data is not multi-component so use the array itself.
        if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_NAME)
        {
          this->GPUMapper->SelectScalarArray(this->ArrayName);
        }
        else if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_ID)
        {
          this->GPUMapper->SelectScalarArray(this->ArrayId);
        }
        this->GPUMapper->SetArrayAccessMode(this->ArrayAccessMode);
        this->GPUMapper->SetScalarMode(this->GetScalarMode());
        this->ConnectMapperInput(this->GPUMapper);
      }
    }
    break;

    case COMPONENT:
    {
      if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_NAME)
      {
        this->GPUMapper->SelectScalarArray(this->ArrayName);
      }
      else if (this->ArrayAccessMode == VTK_GET_ARRAY_BY_ID)
      {
        this->GPUMapper->SelectScalarArray(this->ArrayId);
      }
      this->GPUMapper->SetArrayAccessMode(this->ArrayAccessMode);
      this->GPUMapper->SetScalarMode(this->GetScalarMode());
      this->ConnectMapperInput(this->GPUMapper);

      // GPUMapper supports independent components (separate TFs per component).
      // To follow the current ParaView convention, the first TF is set on
      // the currently selected component. TODO: A more robust future
      // integration of independent components in ParaView should set these
      // TF's already per component.
      vtkVolumeProperty* volProp = vol->GetProperty();
      vtkColorTransferFunction* colortf = volProp->GetRGBTransferFunction(0);
      if (!colortf)
      {
        vtkErrorMacro("Internal Error: No RGBTransferFunction has been set!");
        return;
      }
      volProp->SetColor(this->VectorComponent, colortf);

      vtkPiecewiseFunction* opacitytf = volProp->GetScalarOpacity(0);
      if (!opacitytf)
      {
        vtkErrorMacro("Internal Error: No ScalarOpacity has been set!");
        return;
      }
      volProp->SetScalarOpacity(this->VectorComponent, opacitytf);

      for (int i = 0; i < numComponents; i++)
      {
        double const weight = i == this->VectorComponent ? 1.0 : 0.0;
        volProp->SetComponentWeight(i, weight);
      }
    }
    break;

    default:
      vtkErrorMacro("Unknown vector rendering mode!");
      break;
  }
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ConnectMapperInput(vtkVolumeMapper* m)
{
  assert("pre: m_exists" && m != nullptr);

  bool needShallowCopy = false;
  vtkDataSet* data = m->GetInput();

  if (data == nullptr || data == this->InputDataMagnitude)
  {
    if (vtkImageData::SafeDownCast(this->GetInput()))
    {
      if (vtkUniformGrid::SafeDownCast(this->GetInput()))
      {
        data = vtkUniformGrid::New();
      }
      else
      {
        data = vtkImageData::New();
      }
    }
    else if (vtkRectilinearGrid::SafeDownCast(this->GetInput()))
    {
      data = vtkRectilinearGrid::New();
    }
    m->SetInputDataObject(data);
    needShallowCopy = true;
    data->Delete();
  }
  else
  {
    needShallowCopy =
      ((this->LastInput != this->GetInput()) || (data->GetMTime() < this->GetInput()->GetMTime()));

    m->SetInputDataObject(data);
  }

  if (needShallowCopy)
  {
    data->ShallowCopy(this->GetInput());
    this->LastInput = this->GetInput();
  }
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ConnectFilterInput(vtkImageResample* f)
{
  assert("pre: f_exists" && f != nullptr);

  vtkImageData* input2 = static_cast<vtkImageData*>(f->GetInput());
  bool needShallowCopy = false;
  if (input2 == nullptr)
  {
    // make sure we not create a shallow copy each time to avoid
    // performance penalty.
    input2 = vtkImageData::New();
    f->SetInputDataObject(input2);
    input2->Delete();
    needShallowCopy = true;
  }
  else
  {
    needShallowCopy = ((this->LastFilterInput != this->GetInput()) ||
      (input2->GetMTime() < this->GetInput()->GetMTime()));
  }
  if (needShallowCopy)
  {
    input2->ShallowCopy(this->GetInput());
    this->LastFilterInput = this->GetInput();
  }
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetRequestedRenderMode(int mode)
{
  // If we aren't actually changing it, just return
  if (this->RequestedRenderMode == mode)
  {
    return;
  }

  // Make sure it is a valid mode
  if (mode < vtkSmartVolumeMapper::DefaultRenderMode ||
    mode >= vtkSmartVolumeMapper::UndefinedRenderMode)
  {
    vtkErrorMacro("Invalid Render Mode.");
    return;
  }

  this->RequestedRenderMode = mode;
  this->Modified();
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetRequestedRenderModeToDefault()
{
  this->SetRequestedRenderMode(vtkSmartVolumeMapper::DefaultRenderMode);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetRequestedRenderModeToRayCast()
{
  this->SetRequestedRenderMode(vtkSmartVolumeMapper::RayCastRenderMode);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetRequestedRenderModeToGPU()
{
  this->SetRequestedRenderMode(vtkSmartVolumeMapper::GPURenderMode);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetRequestedRenderModeToOSPRay()
{
  this->SetRequestedRenderMode(vtkSmartVolumeMapper::OSPRayRenderMode);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::ReleaseGraphicsResources(vtkWindow* w)
{
  this->RayCastMapper->ReleaseGraphicsResources(w);
  this->GPUMapper->ReleaseGraphicsResources(w);
  this->GPULowResMapper->ReleaseGraphicsResources(w);

  this->Initialized = 0;
  this->GPUSupported = 0;
  this->RayCastSupported = 0;
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetInterpolationModeToNearestNeighbor()
{
  this->SetInterpolationMode(VTK_RESLICE_NEAREST);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetInterpolationModeToLinear()
{
  this->SetInterpolationMode(VTK_RESLICE_LINEAR);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetInterpolationModeToCubic()
{
  this->SetInterpolationMode(VTK_RESLICE_CUBIC);
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::CreateCanonicalView(vtkRenderer* ren, vtkVolume* volume,
  vtkVolume* volume2, vtkImageData* image, int blend_mode, double viewDirection[3],
  double viewUp[3])
{
  this->ComputeRenderMode(ren, volume);

  if (this->CurrentRenderMode == vtkSmartVolumeMapper::GPURenderMode)
  {
    vtkVolumeProperty* savedProperty = volume->GetProperty();
    volume->SetProperty(volume2->GetProperty());
    volume->GetProperty()->Modified();
    volume->GetProperty()->GetScalarOpacity()->Modified();
    volume->GetProperty()->GetRGBTransferFunction()->Modified();
    this->GPUMapper->CreateCanonicalView(ren, volume, image, blend_mode, viewDirection, viewUp);
    volume->SetProperty(savedProperty);
    volume->GetProperty()->Modified();
    volume->GetProperty()->GetScalarOpacity()->Modified();
    volume->GetProperty()->GetRGBTransferFunction()->Modified();
  }
  else if (this->RayCastSupported)
  {
    this->RayCastMapper->CreateCanonicalView(volume2, image, blend_mode, viewDirection, viewUp);
  }
  else
  {
    vtkErrorMacro("Could not create image - no available mapper");
  }
}

//------------------------------------------------------------------------------
int vtkSmartVolumeMapper::GetLastUsedRenderMode()
{
  return this->CurrentRenderMode;
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);

  os << "FinalColorWindow: " << this->FinalColorWindow << endl;
  os << "FinalColorLevel: " << this->FinalColorLevel << endl;
  os << "RequestedRenderMode: " << this->RequestedRenderMode << endl;
  os << "InteractiveUpdateRate: " << this->InteractiveUpdateRate << endl;
  os << "InteractiveAdjustSampleDistances: " << this->InteractiveAdjustSampleDistances << endl;
  os << "InterpolationMode: " << this->InterpolationMode << endl;
  os << "MaxMemoryInBytes:" << this->MaxMemoryInBytes << endl;
  os << "MaxMemoryFraction:" << this->MaxMemoryFraction << endl;
  os << "AutoAdjustSampleDistances: " << this->AutoAdjustSampleDistances << endl;
  os << indent << "SampleDistance: " << this->SampleDistance << endl;
}

//------------------------------------------------------------------------------
void vtkSmartVolumeMapper::SetVectorMode(int mode)
{
  int const clampedMode = mode < -1 ? -1 : (mode > 1 ? 1 : mode);
  if (clampedMode != this->VectorMode)
  {
    if (clampedMode == MAGNITUDE)
    {
      this->InputDataMagnitude->Modified();
    }

    this->VectorMode = clampedMode;
    this->Modified();
  }
}